The filler heater of the present invention forms a part of the system or process for manufacturing roofing shingles. Roofing shingles of the type contemplated herein are composed of a carrier web, either mineral or organic, sealed with asphalt and coated with asphalt stabilized with mineral filler. A mineral surfacing material is provided on the web and the web is finally surfaced with slate granules. The asphalt stabilized with the mineral filler generally comprises approximately 55% of the total weight of the roofing shingle.
In the process of producing the shingle, the carrier web is first sealed by passing it through a hot bath of asphalt. The fume emissions generated from the hot bath contain pollutants which must be removed before discharge to the atmosphere. These pollutants develop from the normal vaporization of the hot asphalt, the moisture in the carrier web which is vaporized to steam as it passes through the hot asphalt and churning of the hot asphalt by the movement of the web. These fumes or pollutants are collected in a hood enclosure which is ducted to a thermal oxidizer for thorough resolution of all hydrocarbons. The heated fumes are passed over a series of asphalt ducts or tubes to heat the asphalt as it passes to the asphalt bath. The waste heat from the thermal oxidizer is then ducted to a mineral filler heater.
The web, which has now been sealed with asphalt, is then coated with asphalt stabilized with mineral filler. This coating process is critical since it requires a controlled asphalt viscosity in order to achieve uniformity in the distribution of the stabilized asphalt onto the web. Adding mineral filler at ambient temperature in large quantities to the asphalt without having control of the filler temperature will result in wide variances in the asphalt temperature. The percentage of mineral filler added to the heated asphalt has been limited because of this drop in temperature of the stabilized asphalt below the required application temperature as a result of the addition of cooled filler.